Evolution of the Malvinas Plate South of Africa

• Main Authors: Marks, K. M., Stock, J. M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer Verlag 2001
• Subjects: Agulhas Basin; gravity anomalies; Late Cretaceous; Malvinas Plate; plate tectonics; reconstruction; South Atlantic Ocean.; Antarctic; The Antarctic; Antarc*; Antarctica; South Atlantic Ocean
• Online Access: https://doi.org/10.1023/A:1014638325616

We confirm that a Malvinas Plate is required in the Agulhas Basin during the Late Cretaceous because: (1) oblique Mercator plots of marine gravity show that fracture zones generated on the Agulhas rift, as well as the Agulhas Fracture Zone, do not lie on small circles about the 33o-28y South America-Africa stage pole and were therefore not formed by South America-Africa spreading, (2) the 33o-28y South America-Africa stage rotation does not bring 33o magnetic anomalies on the Malvinas Plate into alignment with their conjugates on the African Plate, and (3) errors in the 33o-28y South America-Africa stage rotation cannot account for the misalignment. We present improved Malvinas-Africa finite rotations determined by interpreting magnetic anomaly data in light of fracture zones and extinct spreading rift segments (the Agulhas rift) that are clearly revealed in satellite-derived marine gravity fields covering the Agulhas Basin. The tectonic history of the Malvinas Plate is chronicled through gravity field reconstructions that use the improved Malvinas-Africa finite rotations and more recent South America-Africa and Antarctica-Africa finite rotations. Newly-mapped triple junction traces on the Antarctic, South American, Malvinas, and African Plates, combined with geometric and magnetic constraints observed in the reconstructions, enable us to investigate the locations of the elusive western and southern boundaries of the Malvinas Plate. © 2002 Kluwer Academic Publishers. Received 20 March 2001; accepted 2 October 2001. This revised version was published online in November 2006 with corrections to the Cover Date. The comments of two anonymous reviewers greatly improved this manuscript. We thank Steve Cande for digital magnetic anomaly identifications in the South Atlantic Ocean. J. Stock's participation was supported by NSF grant OPP-9814579. California Institute of Technology, Division of Geological and Planetary Sciences, contribution 8839. Images of the reconstructions are available on the Worldwide Web site ...